Sync allows you to easily set a timer for a video and let it play automatically.
Since Sync is a web application, the video must be compatible with a HTML5 video player. You will need a tool to convert local unsupported files and it's easy. See below.
Open Sync.
Input the video source URL in the textbox (not the website URL). You can preview the video in the player above.
Or, press Alt-S to select the video and subtitle (optional) from your local computer.
You can use Alt-S to toggle between those two input modes.
When finished, click the Confirm button.
Click on the left time-picker to choose a timestamp within the video's duration, this is where the video will begin to play.
Click on the right time-picker to choose a local time, this is when the video will start playing. If you choose a time before the current time, Sync will assume that it's for the next day.
Click the Confirm button when you are ready.
Now you should see a big countdown for your video. This means you entered the Screen Mode, and the video will play itself all the way to the end when countdown goes to 0. In this mode, you cannot pause the video, and all controls (including cursor) are hided.
However, you can exit the Screen Mode at any time by simply pressing esc. The video will be paused at the time you exit Screen Mode for you to set another timer.
To switch to another video, simply refresh the page and you will go back to Step 1.
Download FFmpeg, add its bin folder to your PATH environment variable.
Navigate to your source video, use the following command to convert a .mkv file to a .mp4 file and extract the subtitle.
ffmpeg -i yourSource.mkv -c:v h264 -c:a aac output.mp4 -c:s webvtt subtitle.vtt
Depending on your source video's encodings and length, this could take several minutes.
Or, to do these things separately:
ffmpeg -i yourSource.mkv -c:v h264 -c:a aac output.mp4
ffmpeg -i yourSource.mkv -vn -an -c:s webvtt subtitle.vtt
Your can even specify which audio or subtitle to extract if there're multiple. To do this, use ffprobe yourSource.mkv to list all stream channels, find the one you want, and use the -map option. For example, if you want the second subtitle (usually it's in stream #0:3), use:
ffmpeg -i yourSource.mkv -map 0:3 -vn -an -c:s webvtt subtitle2.vtt
You can refer to the FFmpeg guide for more details.
Used Element Plus for some UI components.